Philip Hammond: Brexit will leave UK economy worse off
https://www.bbc.co.uk/news/uk-politics-46366162
What this actually means is that the 'cost' to GDP in ten years' time of foregoing half a million extra migrant workers is a couple of pounds a week per head.
Sounds like a bargain to me compared to the cost of extra housing, health, education, roads etc needed to cope with a continued influx of Eastern European 'coolies' to pick our cauliflowers.